【作者】 陆连玉；

【导师】 姜忠义；

【作者基本信息】 天津大学 ， 化学工艺， 2008， 博士

【摘要】 乳酸乙酯作为一种极具开发价值和应用前景的绿色溶剂,其传统脱水生产工艺存在脱水温度高、能耗大、原料损耗大、费用高等缺点,有必要开发具有节能降耗减排特点的新工艺,使其既有较高的乳酸乙酯产率,又能实现低温度、低能耗和低成本生产。渗透蒸发-酯化反应耦合工艺以其绿色、高效、节能的突出特点而具有重要的研发价值,渗透蒸发技术应用于酯化反应脱水体系的关键技术是高性能渗透蒸发脱水膜的研制。本论文以壳聚糖（CS）为主体膜材料,制备了壳聚糖-无机杂化膜（包括CS/SiO₂和CS/TiO₂杂化膜）、改性壳聚糖交联膜（q-CS/GA交联膜）和改性壳聚糖-无机杂化膜（q-CS/TiO₂杂化膜）。并采用FTIR、SEM、XRD、DMA、TG、DSC和接触角测定等方法对制备的渗透蒸发脱水膜进行了表征。系统研究了膜的溶胀吸附、渗透蒸发脱水性能和其对乳酸和乙醇酯化耦合反应的影响。论文重点考察了有机-无机杂化、季铵化、交联等改性手段对壳聚糖膜的物理化学性质、形态结构和溶胀吸附性能的影响,进而研究了对壳聚糖膜渗透蒸发脱水性能的影响以及对酯化反应的影响。无机纳米粒子的引入、壳聚糖-NH2中取代基-（CH3）3Cl的引入以及戊二醛交联剂的加入破坏了壳聚糖高分子间的氢键作用,使得膜的亲水性增加,结晶度减小,渗透蒸发脱水性能得到一定提高,对乳酸和乙醇酯化反应生成乳酸乙酯的产率有明显促进作用。使用CS/SiO₂（02）、CS/TiO₂（06）杂化膜、q-CS/GA（1.5）交联膜和q-CS/TiO₂（06）杂化膜的酯化反应-渗透蒸发耦合过程的乳酸乙酯产率分别为79.9、78.2、80.7、78.8wt.%,而使用纯壳聚糖膜的耦合过程乳酸乙酯产率为65.5wt.%,没有与渗透蒸发过程耦合的酯化反应酯产率仅为60.8wt.%。采用分子动力学模拟方法建立了壳聚糖-SiO₂杂化膜的结构模型,研究了壳聚糖和SiO₂无机粒子间的相互作用、壳聚糖-SiO₂杂化膜的自由体积特性及无机粒子的加入对水和乙醇在膜中扩散过程的影响。结果表明杂化膜内能够容纳乙醇分子的自由体积分数降低程度远大于能够容纳水分子的自由体积空穴分数,使得杂化膜扩散选择性明显升高,且SiO₂粒子越小,扩散选择性增加越明显。更多还原

【Abstract】 Ethyl lactate, as a green solvent, has great development value and application prospect, its traditional production method suffer from a lot of drawbacks including the high temperature of dehydration, high consumption of energy and raw material and high cost. It is important to develop new technologies which dominated with high yield of ethyl lactate, low temparature, low consumption of energy and low cost. Recently, it was found that pervaporation-assisted esterification process has important research value because of its outstanding features including green technology, high effiency and low consumption of energy.The key technique of this coupling prosess is to develop a pervaporation membrane with excellent dehydration performance.In this study, chitosan was used as the bulk membrane material and the chitosan organic-inorganic hybrid membranes （including CS/SiO₂ and CS/TiO₂ hybrid membranes）, the cross-linking modified chitosan membranes （the cross-linking q-CS/GA membrane） and the modified chitosan organic-inorganic hybrid membranes （q-CS/TiO₂ hybrid membrane） were developed. The prepared membranes were characterized by FTIR, SEM, XRD, DMA, TG/DTG, DSC, the measurement of contact angel and some other methods. The swollen and adsorption performance of these membranes, the dehydration performance of pervaporation and its function in the esterification of lactic acid and ethanol coupled with pervaporation were investigated.Furthermore, the effects of modification methods, such as organic-inorganic hybridization, quaternization and cross-linking, on the physicochemical properties, the configuration and structure and the swollen and adsorption performance of chitosan membrane were studied. Then, the dehydration performance of these modified chitosan membranes for pervaporation and esterification were investigated. It was found that, the hydrogen-bonding interaction between the chitosan moleculs was destroyed by introducing the inorganic nanparticles, the substituting group -（CH3）3Cl of -NH2 and the glutaric dialdehyde as the cross-linking agent. These factors resulted in the increasing hydrophilicity of membrane, the decrease of crystallinity and the increase of the membranes’pervaporating dehydration perfomance, consequently, the esterification of lactic acid of ethanol was enhanced. As a result, the yield of ethyl lactate in pervaporation-assisted esterifaction of lactic acid and ethanol could increased to 79.9, 78.2, 80.7 and 78.8wt% by using CS/SiO₂（02）, CS/TiO₂（06） hybrid membrane, q-CS/GA（1.5） cross-linked membrane and q-CS/TiO₂（06） hybrid membrane, meanwhile, the yield of ethyl lactate by using chitosan membrane was 65.5wt%, which was only 60.8% without pervaporation.Using molecular dynamics simulation technique, the structure model of chitosan- SiO₂ hybrid membrane was constructed. The interaction between chitosan and SiO₂ particles was investigated. Next, the free volume properties of chitosan membrane and chitosan-SiO₂ membranes and the effect of introducing inorganic particles on the diffusion process of water and ethanol in chitosan hybrid membrane were studied. It suggested that the fractional free volume of hybrid membrane for ethanol molecule was decreased much more than that for the water molecule, accordingly, the diffusion selectivity of hybrid membrane increased more remarkably. Moreover, the smaller the SiO₂ particles, the more evidently the diffusion selectivity can increase.更多还原